The yen has fallen to above 120 yen against the dollar and as low as 163 yen against the euro. Although a weak yen and strong dollar are often confused as the same thing, what we're looking at today is a weak, yen not a strong dollar.
A currency exchange rate is a rate of conversion between two currencies. A comparison of two currencies alone will not easily show whether one is strong or the other weak, but a comparison with a third currency (like the gold standard under the postwar regime led by the International Monetary Fund) will make it easier to determine the positions of both.
The yen is currently declining against both the dollar and the euro, with the dollar declining against the euro, underlining the yen's weakness.